1  ---
  2  Name: FerrisProof
  3  Type: Product Requirements Document
  4  Status: Draft
  5  Date: 2025-12-31
  6  ---
  7  
  8  # FerrisProof
  9  
 10  ## Introduction
 11  
 12  FerrisProof is a multi-layer correctness pipeline for Rust applications that combines formal modeling (TLA+, Alloy), Rust's type system, and property-based testing to ensure systems are memory-safe, structurally sound, and functionally correct. The system operates across four verification layers with progressive adoption and configurable enforcement levels.
 13  
 14  ## Glossary
 15  
 16  - **FerrisProof**: The complete multi-layer correctness pipeline system
 17  - **Verification_Level**: Progressive maturity levels (minimal, standard, strict, formal)
 18  - **Configuration_Manager**: System for managing hierarchical verification configurations
 19  - **Formal_Specification**: TLA+ or Alloy models for protocol-level verification
 20  - **Session_Types**: Type-level protocol correctness via typestate patterns
 21  - **Property_Based_Testing**: Runtime invariant verification using generated test cases
 22  - **CLI_Tool**: Command-line interface for configuration and verification management
 23  - **Enforcement_Mode**: How violations are handled (advisory, warning, error)
 24  - **Verification_Artifact**: Generated files (tests, types, reports) produced by FerrisProof
 25  - **Counterexample**: Concrete input/state that violates a specification or property
 26  - **Typestate**: Pattern where types encode valid state transitions
 27  - **Model_Checker**: External tool (TLC, Alloy Analyzer) that verifies formal specifications
 28  - **Refinement_Type**: Type with additional predicates constraining valid values
 29  - **Property_Generator**: Function producing test inputs for property-based testing
 30  - **Invariant**: Condition that must hold across all valid system states
 31  - **Temporal_Property**: Specification about system behavior over time (safety/liveness)
 32  
 33  ## Requirements
 34  
 35  ### Requirement 1: Multi-Layer Verification Architecture [MUST HAVE]
 36  
 37  **User Story:** As a Rust developer, I want a layered verification system, so that I can catch different classes of errors at appropriate abstraction levels.
 38  
 39  #### Acceptance Criteria
 40  
 41  1. THE FerrisProof SHALL implement four distinct verification layers
 42  2. WHEN Layer 1 is enabled, THE Formal_Specification SHALL model protocol-level invariants and concurrency patterns
 43  3. WHEN Layer 2 is enabled, THE Session_Types SHALL enforce protocol correctness via typestate
 44  4. WHEN Layer 3 is enabled, THE Property_Based_Testing SHALL verify runtime invariants through generated test cases
 45  5. WHEN Layer 4 is enabled, THE Production_Monitoring SHALL provide observability and runtime assertions
 46  6. THE FerrisProof SHALL allow selective layer activation based on verification level
 47  7. WHEN Layer 3 tests fail, THE FerrisProof SHALL suggest Layer 1 specification review
 48  8. WHEN Layer 2 type errors occur, THE FerrisProof SHALL link to relevant Layer 1 specifications if available
 49  9. THE FerrisProof SHALL support selective layer execution with dependency checking
 50  10. THE FerrisProof SHALL prevent Layer 2 execution if Layer 1 verification fails when formal level is active
 51  
 52  ### Requirement 2: Hierarchical Configuration System [MUST HAVE]
 53  
 54  **User Story:** As a project maintainer, I want configurable verification levels, so that I can balance development velocity with correctness guarantees.
 55  
 56  #### Acceptance Criteria
 57  
 58  1. THE Configuration_Manager SHALL support four verification levels: minimal, standard, strict, formal
 59  2. WHEN minimal level is set, THE FerrisProof SHALL enable only type safety and basic tests
 60  3. WHEN standard level is set, THE FerrisProof SHALL enable type safety, basic tests, and property-based testing
 61  4. WHEN strict level is set, THE FerrisProof SHALL enable session types, refinement types, and concurrency testing
 62  5. WHEN formal level is set, THE FerrisProof SHALL enable all verification techniques including formal specifications
 63  6. THE Configuration_Manager SHALL support module-level overrides for granular control
 64  7. THE Configuration_Manager SHALL support item-level attribute-based configuration
 65  8. THE Configuration_Manager SHALL discover ferrisproof.toml files in subdirectories recursively
 66  9. WHEN multiple configuration files exist, THE Configuration_Manager SHALL merge them with child overriding parent
 67  10. THE Configuration_Manager SHALL validate that module path patterns are valid glob expressions
 68  11. WHEN glob patterns overlap, THE Configuration_Manager SHALL apply most specific match
 69  12. THE Configuration_Manager SHALL cache parsed configurations with file modification time tracking
 70  
 71  ### Requirement 3: Formal Specification Integration [SHOULD HAVE]
 72  
 73  **User Story:** As a systems architect, I want to model high-level protocols before implementation, so that I can catch design flaws in distributed systems and concurrent algorithms.
 74  
 75  #### Acceptance Criteria
 76  
 77  1. THE Formal_Specification SHALL support TLA+ for temporal logic verification
 78  2. THE Formal_Specification SHALL support Alloy for structural modeling with SAT-based verification
 79  3. WHEN a TLA+ specification exists, THE FerrisProof SHALL verify it using the TLC model checker
 80  4. WHEN formal specifications are verified, THE FerrisProof SHALL generate corresponding Rust type scaffolding
 81  5. THE Formal_Specification SHALL link property tests to specification states
 82  6. WHEN specification verification fails, THE FerrisProof SHALL provide structured counterexample reports containing execution trace, violated invariant, minimal reproducing scenario, and suggested fixes within 10 seconds for 90% of failures
 83  
 84  ### Requirement 4: Type-Level Verification System
 85  
 86  **User Story:** As a Rust developer, I want to encode correctness properties in the type system, so that I can prevent entire classes of bugs at compile time.
 87  
 88  #### Acceptance Criteria
 89  
 90  1. THE Session_Types SHALL implement protocol correctness via typestate patterns
 91  2. THE Session_Types SHALL prevent invalid state transitions at compile time
 92  3. THE FerrisProof SHALL support refinement types for value-level constraints via procedural macros
 93  4. WHEN refinement types are used, THE FerrisProof SHALL generate constructors that validate predicates
 94  5. THE FerrisProof SHALL support linear types for resource ownership guarantees
 95  6. THE Session_Types SHALL consume types to prevent reuse after state transitions
 96  
 97  ### Requirement 5: Property-Based Testing Framework
 98  
 99  **User Story:** As a developer, I want comprehensive property-based testing, so that I can verify universal properties across all possible inputs.
100  
101  #### Acceptance Criteria
102  
103  1. THE Property_Based_Testing SHALL integrate with proptest for QuickCheck-style testing
104  2. THE Property_Based_Testing SHALL support Bolero for fuzzing integration
105  3. THE Property_Based_Testing SHALL support Kani for bounded model checking
106  4. WHEN property tests are defined, THE FerrisProof SHALL link them to formal specification invariants
107  5. THE Property_Based_Testing SHALL support metamorphic testing for transformation relationships
108  6. WHEN property tests fail, THE FerrisProof SHALL provide structured counterexamples for debugging
109  
110  ### Requirement 6: Configuration Management and CLI [MUST HAVE]
111  
112  **User Story:** As a project maintainer, I want a command-line tool for managing verification configurations, so that I can easily initialize, upgrade, and validate verification setups.
113  
114  #### Acceptance Criteria
115  
116  1. THE CLI_Tool SHALL support project initialization with configurable verification levels
117  2. THE CLI_Tool SHALL support verification level upgrades with automated migration assistance
118  3. THE CLI_Tool SHALL validate current verification requirements and report violations
119  4. THE CLI_Tool SHALL generate verification artifacts including property tests and session types
120  5. WHEN checking verification requirements, THE CLI_Tool SHALL provide detailed violation reports
121  6. THE CLI_Tool SHALL support dry-run mode for upgrade operations
122  7. THE CLI_Tool SHALL support interactive mode for configuration setup with prompts
123  8. THE CLI_Tool SHALL provide tab completion for bash, zsh, and fish shells
124  9. WHEN violations are found, THE CLI_Tool SHALL display them with color-coded severity
125  10. THE CLI_Tool SHALL support --fix flag to automatically resolve fixable violations
126  11. THE CLI_Tool SHALL provide JSON output for machine parsing via --output json flag
127  12. THE CLI_Tool SHALL respect NO_COLOR environment variable for accessibility
128  
129  ### Requirement 7: Progressive Adoption Strategy [SHOULD HAVE]
130  
131  **User Story:** As a development team, I want to gradually adopt verification techniques, so that I can improve system correctness without disrupting existing workflows.
132  
133  #### Acceptance Criteria
134  
135  1. THE FerrisProof SHALL support opt-in verification with minimal initial overhead
136  2. WHEN starting adoption, THE FerrisProof SHALL begin with property-based testing only
137  3. THE FerrisProof SHALL provide automated scaffolding generation for verification upgrades
138  4. THE FerrisProof SHALL support module-specific verification level overrides
139  5. WHEN upgrading verification levels, THE FerrisProof SHALL provide automated scaffolding generation for at least 80% of required changes, template files for manual intervention cases, diff preview showing proposed changes before applying, rollback capability if upgrade fails, and estimated time and effort metrics for manual tasks
140  6. THE FerrisProof SHALL maintain backward compatibility during verification level changes
141  
142  ### Requirement 8: CI/CD Integration and Reporting
143  
144  **User Story:** As a DevOps engineer, I want CI/CD integration for verification pipelines, so that I can enforce correctness requirements in automated builds.
145  
146  #### Acceptance Criteria
147  
148  1. THE FerrisProof SHALL integrate with GitHub Actions for automated verification
149  2. THE FerrisProof SHALL support configurable enforcement modes: advisory, warning, error
150  3. WHEN verification violations occur, THE FerrisProof SHALL generate structured reports in multiple formats
151  4. THE FerrisProof SHALL support parallel verification across different verification levels
152  5. THE FerrisProof SHALL provide build artifacts including verification reports and coverage metrics
153  6. WHEN enforcement mode is error, THE FerrisProof SHALL fail builds on verification violations
154  
155  ### Requirement 9: Tool Integration and Extensibility [SHOULD HAVE]
156  
157  **User Story:** As a verification engineer, I want integration with multiple formal verification tools, so that I can choose appropriate tools for different verification tasks.
158  
159  #### Acceptance Criteria
160  
161  1. THE FerrisProof SHALL support TLA+ integration via TLC model checker
162  2. THE FerrisProof SHALL support Alloy integration for structural verification
163  3. THE FerrisProof SHALL support Loom integration for concurrency testing
164  4. THE FerrisProof SHALL provide vendor-neutral APIs for tool integration
165  5. WHEN multiple tools are available, THE FerrisProof SHALL allow tool selection via configuration
166  6. THE FerrisProof SHALL support extensible tool plugins for additional verification backends
167  7. THE FerrisProof SHALL use standard exit codes: 0 (success), 1 (verification failure), 2 (configuration error), 3 (tool unavailable)
168  8. WHEN calling external tools, THE FerrisProof SHALL enforce timeout limits with graceful termination
169  9. THE FerrisProof SHALL capture stdout and stderr from external tools separately
170  10. THE FerrisProof SHALL validate tool output formats before parsing
171  11. WHEN tool versions mismatch expected versions, THE FerrisProof SHALL warn users
172  12. THE FerrisProof SHALL provide plugin API with stable ABI for external tool integrations
173  13. THE Plugin_API SHALL support tool discovery and version checking, configuration schema validation, asynchronous verification task execution, and result serialization/deserialization
174  14. THE FerrisProof SHALL maintain backward compatibility for plugin API across minor versions
175  15. THE FerrisProof SHALL document minimum and maximum supported versions for each external tool
176  16. WHEN tool versions are incompatible, THE FerrisProof SHALL provide clear upgrade/downgrade guidance
177  17. THE FerrisProof SHALL pin tool versions in lock files for reproducible verification
178  18. THE Configuration_Manager SHALL support version-specific configuration overrides
179  
180  ### Requirement 10: Configuration Validation and Error Handling [MUST HAVE]
181  
182  **User Story:** As a developer, I want clear error messages and configuration validation, so that I can quickly resolve verification setup issues.
183  
184  #### Acceptance Criteria
185  
186  1. THE Configuration_Manager SHALL validate configuration files on load
187  2. WHEN configuration errors exist, THE FerrisProof SHALL provide detailed error messages with suggested fixes
188  3. THE FerrisProof SHALL validate tool availability before attempting verification
189  4. WHEN verification tools are missing, THE FerrisProof SHALL provide installation guidance
190  5. THE Configuration_Manager SHALL detect configuration conflicts and suggest resolutions
191  6. THE FerrisProof SHALL provide configuration templates for common project types
192  7. WHEN TLA+ model checking times out, THE FerrisProof SHALL allow partial result inspection
193  8. WHEN property tests find counterexamples, THE FerrisProof SHALL support automatic test case shrinking
194  9. WHEN conflicting module-level overrides exist, THE FerrisProof SHALL use most specific path match
195  10. WHEN verification tools crash, THE FerrisProof SHALL capture crash logs and suggest troubleshooting steps
196  11. THE FerrisProof SHALL validate that formal specifications are syntactically correct before running model checkers
197  12. WHEN cargo build fails, THE FerrisProof SHALL NOT attempt verification and SHALL report build errors clearly
198  
199  ### Requirement 11: Performance and Resource Constraints [MUST HAVE]
200  
201  **User Story:** As a developer, I want verification to complete within reasonable time bounds, so that it doesn't block development workflows.
202  
203  #### Acceptance Criteria
204  
205  1. WHEN running property-based tests at standard level, THE FerrisProof SHALL complete within 5 minutes for projects under 50k LOC
206  2. WHEN running TLA+ model checking, THE FerrisProof SHALL support configurable timeout limits
207  3. THE FerrisProof SHALL cache verification results to avoid redundant computation
208  4. WHEN verification cache is valid, THE FerrisProof SHALL complete incremental checks within 30 seconds
209  5. THE Configuration_Manager SHALL limit memory usage to under 2GB for standard verification levels
210  6. THE FerrisProof SHALL provide progress indicators for long-running verification tasks
211  
212  ### Requirement 12: Security and Privacy [MUST HAVE]
213  
214  **User Story:** As a security engineer, I want verification tools to handle sensitive code safely, so that proprietary algorithms and secrets remain protected.
215  
216  #### Acceptance Criteria
217  
218  1. THE FerrisProof SHALL NOT transmit code or specifications to external services without explicit consent
219  2. WHEN formal specifications contain sensitive information, THE FerrisProof SHALL support local-only verification
220  3. THE CLI_Tool SHALL NOT log sensitive data in verification reports
221  4. THE FerrisProof SHALL support air-gapped environments for classified codebases
222  5. WHEN generating reports, THE FerrisProof SHALL sanitize paths and module names if configured
223  6. THE FerrisProof SHALL document all external tool dependencies and their data handling policies
224  
225  ### Requirement 13: Platform Compatibility and Portability [SHOULD HAVE]
226  
227  **User Story:** As a cross-platform developer, I want FerrisProof to work consistently across operating systems, so that teams can use their preferred development environments.
228  
229  #### Acceptance Criteria
230  
231  1. THE FerrisProof SHALL support Linux, macOS, and Windows
232  2. WHEN running on Windows, THE FerrisProof SHALL provide native Windows path handling
233  3. THE FerrisProof SHALL support both glibc and musl libc targets on Linux
234  4. THE CLI_Tool SHALL provide consistent behavior across all supported platforms
235  5. WHEN platform-specific tools are unavailable, THE FerrisProof SHALL provide graceful degradation
236  6. THE FerrisProof SHALL document platform-specific limitations and workarounds
237  
238  ### Requirement 14: Observability and Debugging [SHOULD HAVE]
239  
240  **User Story:** As a developer debugging verification failures, I want detailed logs and traces, so that I can understand why verification failed.
241  
242  #### Acceptance Criteria
243  
244  1. THE FerrisProof SHALL support configurable log levels: error, warn, info, debug, trace
245  2. WHEN verification fails, THE FerrisProof SHALL log the complete command that was executed
246  3. THE FerrisProof SHALL provide structured JSON logs for machine parsing
247  4. WHEN running in CI, THE FerrisProof SHALL automatically enable verbose logging
248  5. THE CLI_Tool SHALL support --explain <error-code> to show detailed explanations
249  6. THE FerrisProof SHALL track and report verification metrics including total verification time per layer, number of test cases executed, cache hit rate, and memory usage per verification task
250  7. WHEN multiple verification tasks run concurrently, THE FerrisProof SHALL provide task-level progress tracking
251  
252  ### Requirement 15: Data Model and Serialization [SHOULD HAVE]
253  
254  **User Story:** As a tool integrator, I want standardized data formats, so that I can build tooling around FerrisProof outputs.
255  
256  #### Acceptance Criteria
257  
258  1. THE Configuration_Manager SHALL use TOML for configuration files (ferrisproof.toml)
259  2. THE FerrisProof SHALL support JSON Schema validation for configuration files
260  3. WHEN generating reports, THE FerrisProof SHALL support JSON, Markdown, and HTML output formats
261  4. THE FerrisProof SHALL use semantic versioning for configuration schema versions
262  5. THE FerrisProof SHALL provide schema migration tools when configuration format changes
263  6. THE Verification_Results SHALL include timestamp (ISO 8601 format), Git commit hash if available, configuration snapshot used, per-layer success/failure status, and detailed failure diagnostics
264  7. THE FerrisProof SHALL store verification cache using content-addressed storage
265  8. THE FerrisProof SHALL support exporting verification history for audit trails
266  
267  ### Requirement 16: Backward Compatibility and Versioning [COULD HAVE]
268  
269  **User Story:** As a project maintainer, I want stable APIs and migration paths, so that FerrisProof upgrades don't break existing projects.
270  
271  #### Acceptance Criteria
272  
273  1. THE FerrisProof SHALL follow semantic versioning (SemVer 2.0)
274  2. WHEN breaking changes occur in major versions, THE FerrisProof SHALL provide migration guides
275  3. THE FerrisProof SHALL maintain configuration format compatibility within major versions
276  4. THE CLI_Tool SHALL support --version flag showing FerrisProof and all tool versions
277  5. THE FerrisProof SHALL detect configuration schema version and auto-migrate if possible
278  6. WHEN auto-migration fails, THE FerrisProof SHALL provide step-by-step manual migration instructions
279  7. THE FerrisProof SHALL support running multiple versions side-by-side via container isolation
280  
281  ### Requirement 17: Documentation and User Guidance [MUST HAVE]
282  
283  **User Story:** As a new FerrisProof user, I want comprehensive documentation, so that I can understand and use the tool effectively.
284  
285  #### Acceptance Criteria
286  
287  1. THE FerrisProof SHALL provide getting-started guide with step-by-step examples
288  2. THE FerrisProof SHALL document all configuration options with type information and examples
289  3. THE FerrisProof SHALL provide migration guide for each verification level transition
290  4. THE FerrisProof SHALL include example projects demonstrating each verification level
291  5. THE FerrisProof SHALL maintain API documentation with minimum 80% coverage
292  6. THE FerrisProof SHALL provide troubleshooting guide for common errors
293  7. THE Documentation SHALL be versioned alongside code releases
294  8. THE FerrisProof SHALL support ferris-proof docs command to open local documentation
295  
296  ### Requirement 18: Self-Verification and Testing [MUST HAVE]
297  
298  **User Story:** As a contributor, I want FerrisProof itself to be well-tested, so that I can trust its verification results.
299  
300  #### Acceptance Criteria
301  
302  1. THE FerrisProof SHALL maintain minimum 80% code coverage
303  2. THE FerrisProof SHALL include integration tests for each verification layer
304  3. THE FerrisProof SHALL verify its own configuration parsing logic with property tests
305  4. THE FerrisProof SHALL include regression tests for all fixed bugs
306  5. THE FerrisProof SHALL run its own verification pipeline at formal level
307  6. THE FerrisProof SHALL include performance benchmarks to detect regressions
308  7. THE Test_Suite SHALL complete in under 10 minutes on standard CI runners
309  
310  ### Requirement 19: Supply Chain Security [SHOULD HAVE]
311  
312  **User Story:** As a security-conscious organization, I want to verify FerrisProof's integrity, so that I can trust it in secure environments.
313  
314  #### Acceptance Criteria
315  
316  1. THE FerrisProof releases SHALL be signed with GPG keys
317  2. THE FerrisProof SHALL publish cryptographic checksums (SHA256) for all release artifacts
318  3. THE FerrisProof SHALL maintain Software Bill of Materials (SBOM) in SPDX format
319  4. THE FerrisProof SHALL document all external tool dependencies with version ranges
320  5. THE FerrisProof SHALL provide reproducible builds via Nix or Docker
321  6. THE FerrisProof SHALL disclose security vulnerabilities within 7 days of confirmation
322  7. THE FerrisProof SHALL support SLSA Level 3 provenance for releases